U.S. patent application number 11/068980 was filed with the patent office on 2005-09-08 for arrangement for the generation of sonic fields of a specific modal composition.
Invention is credited to Arnold, Frank, Holste, Fredi, Moore, Alastair D., Rose, Marco.
Application Number | 20050194206 11/068980 |
Document ID | / |
Family ID | 34746054 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050194206 |
Kind Code |
A1 |
Rose, Marco ; et
al. |
September 8, 2005 |
Arrangement for the generation of sonic fields of a specific modal
composition
Abstract
A device for simulating sound produced by certain equipment, for
example a rotor-stator arrangement of a turbomachine, or for
generation of opposing sound fields for active sound control,
including active sound reduction and active sound amplification,
comprises flow obstacles (2) provided in a flow duct (1) flown by a
fluid at which vortices (5, 6) are shed at a certain frequency
depending on the shape and size of the flow obstacles and the
velocity of flow. The quantity and spatial arrangement of the flow
obstacles is selected such that a periodically spatially and
temporally changing pressure field for the excitation of a sound
field (8) of a certain modal content is produced by the entirety of
the vortices shed. This sound field reacts synchronizingly on the
vortex shedding. The resonant circuit so formed, whose vortex
shedding frequency is in the range of the resonant frequency of the
sound field to be excited, is the sound source.
Inventors: |
Rose, Marco; (Freiberg,
DE) ; Holste, Fredi; (Berlin, DE) ; Arnold,
Frank; (Berlin, DE) ; Moore, Alastair D.;
(Derby, GB) |
Correspondence
Address: |
Harbin King & Klima
500 Ninth Street SE
Washington
DC
20003
US
|
Family ID: |
34746054 |
Appl. No.: |
11/068980 |
Filed: |
March 2, 2005 |
Current U.S.
Class: |
181/224 ;
181/214 |
Current CPC
Class: |
G10K 11/178 20130101;
G10K 15/04 20130101; G10K 2210/3212 20130101 |
Class at
Publication: |
181/224 ;
181/214 |
International
Class: |
E04F 017/04; F02K
011/00; B64D 033/02 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 3, 2004 |
EP |
EP04090083.9 |
Claims
What is claimed is:
1. A device for generating sound fields of a specific modal
composition; comprising: a flow duct flown by a fluid; at least one
flow obstacle positioned in the flow duct for creating and
periodically shedding vortices at a certain shedding frequency
depending on the shape and size of the at least one flow obstacle
and a velocity of the fluid flow, the number and spatial
arrangement of the at least one flow obstacle being selected such
that a periodically spatially and temporally changing pressure
field for the excitation of a sound field of a certain modal
composition is produced by the entirety of the shed vortices which
reacts synchronizingly on the vortex shedding, with a resultant
resonant circuit, whose vortex shedding frequency is in a range of
a resonant frequency of the sound field to be excited.
2. A device in accordance with claim 1, comprising several flow
obstacles positioned at intervals in at least one cross-sectional
plane of the flow duct.
3. A device in accordance with claim 2, wherein the flow obstacles
are projections projecting out from an inner wall of the flow duct,
and are profiled such that periodic shedding of vortices create a
vortex path, as well as the respective modal sound field.
4. A device in accordance with claim 3, wherein the projections
comprise a stay having at least one vortex shedding portion spaced
from the inner wall of the flow duct, the stay being profiled such
that it produces at most, only negligible vortex shedding.
5. A device in accordance with claim 2, wherein the flow obstacles
are cavities formed into an inner wall of the flow duct.
6. A device in accordance with claim 1, wherein the fluid is one of
a cold gas and a hot gas.
7. A device in accordance with claim 1, and further comprising
means for vibration excitation to control a phase relation of
vortex shedding at the flow obstacles.
8. A device in accordance with claim 1, comprising several flow
obstacles that are adjustable in several axes.
9. A device in accordance with claim 2, wherein the several flow
obstacles are positioned at regular intervals.
10. A device in accordance with claim 2, wherein the several flow
obstacles are positioned at irregular intervals.
11. A device in accordance with claim 2, wherein the several flow
obstacles are positioned in multiple circumferential planes.
12. A device in accordance with claim 2, wherein the several flow
obstacles are positioned in multiple planes in a direction of fluid
flow.
13. A device in accordance with claim 3, wherein the projections
comprise a stay having a plurality of vortex shedding portions
spaced from each other, the stay being profiled such that it
produces at most, only negligible vortex shedding.
14. A device in accordance with claim 4, wherein the projections
comprise a stay having a plurality of vortex shedding portions
spaced from each other.
15. A device in accordance with claim 4, wherein the several flow
obstacles are positioned at regular intervals.
16. A device in accordance with claim 4, wherein the several flow
obstacles are positioned at irregular intervals.
17. A device in accordance with claim 4, wherein the several flow
obstacles are positioned in multiple circumferential planes.
18. A device in accordance with claim 4, wherein the several flow
obstacles are positioned in multiple planes in a direction of fluid
flow.
19. A device in accordance with claim 1, wherein the device
performs at least one of simulating a sound produced by
rotor-stator arrangements of turbomachines, active sound
amplification, and creating an opposing sound field for active
sound reduction.
20. A device in accordance with claim 1, wherein the fluid is a
liquid.
Description
[0001] This application claims priority to European Patent
Application EP04090083.9 filed Mar. 3, 2004, the entirety of which
is incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] This invention relates to an arrangement for the generation
of sound fields of a specific modal composition as simulated sound
source for acoustic investigations, in particular for the
simulation of the sound produced by rotor-stator arrangements of
turbomachines, for active sound amplification, or as an opposing
sound field for active sound reduction.
[0003] In many technical sectors, the application and operation of
certain equipment, for example aircraft propulsion units,
automobile drive units, compressors, gas turbines, venting systems,
fans and the like, involves an undesired, aero-acoustic sound
level. With such equipment, for example rotor-stator systems of
compressors and gas turbines, the performance of investigations
into the causes of generation and propagation of air-borne noise or
into measures for noise attenuation using a real-life test
arrangement involves considerable technical investment. In the case
of turbomachines, such investigations can be performed with
rotor-stator arrangements which, due to the necessary drive units,
the moving components, the high weight and the required control
mechanisms, are complicated and expensive. In addition, the
generation of a simulated sound field for test purposes or as
opposing sound field for active sound reduction, as described, for
example, in U.S. Specifications U.S. Pat. No. 5,702,230 or U.S.
Pat. No. 5,590,849, also requires considerable apparatus, control
and energetic investment for the provision and operation of active
elements, such as loudspeakers or piezo-electric sound sources.
Additional problems arise from the provision of powerful actuators,
their high weight, power demand and operation at elevated
temperatures, pressures and velocities of flow.
BRIEF SUMMARY OF THE INVENTION
[0004] The present invention, in a broad aspect, provides an
arrangement for the generation of sound fields of specific modal
content, hereinafter referred to as mode generator, for application
as simulated sound source for scientific-technical investigations,
for active sound amplification or as an opposing sound field for
active sound reduction which is simply designed and inexpensively
producible and operable.
[0005] It is a particular object of the present invention to
provide solution to the above problems by equipment designed in
accordance with the features of described herein. Further objects
and advantages of the present invention will become apparent from
the description below.
[0006] In other words, the idea underlying the present invention is
the provision of a mode generator comprising a flow duct which is
passed by a fluid, in particular a gas, and of flow obstacles
arranged within this flow duct. The flow obstacles are designed
such that they shed vortices from the flow medium. The shape and
size of the flow obstacles and the velocity of flow within the flow
duct are selected such that a certain vortex shedding frequency is
not undershot. The quantity and spatial arrangement of the flow
obstacles is such that a pressure field is produced by the entirety
of the vortices shed which periodically changes in time and space.
This pressure field excites a sound field of specific modal
composition which synchronizingly reacts on the vortex shedding.
The feedback-caused resonant circuit so produced, whose vortex
shedding frequency is in the range of the resonant frequency of the
sound field, is a sound source. Accordingly, a sound wave for
specific acoustic investigations can be simulated in the simplest
manner, such as for example, a sound wave for the stator-rotor
arrangement in the case of turbo-engine investigations. Similarly,
this simple and cost-effective arrangement enables active sound
control, including active sound amplification, and generation of
opposing sound fields for active sound reduction. The present
arrangement allows the apparatus, weight and cost investment to be
reduced significantly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The present invention is more fully described in the light
of the accompanying drawings showing preferred embodiments. In the
drawings,
[0008] FIG. 1 is a side view of an arrangement according to the
present invention for the generation of modal sound fields
(aero-acoustic mode generator),
[0009] FIG. 2 is a longitudinal section of the arrangement
according to FIG. 1,
[0010] FIG. 3 is a perspective view of the arrangement according to
FIG. 1,
[0011] FIG. 4 is a side view of another embodiment of an
arrangement for the generation of modal sound fields,
[0012] FIG. 5 is a longitudinal section of the arrangement
according to FIG. 4,
[0013] FIG. 6 is a perspective view of a flow obstacle in
accordance with the embodiment of FIG. 4,
[0014] FIG. 7 is a sectional view of the stay of the flow obstacle
according to FIG. 6,
[0015] FIG. 8 is a sectional view of the vortex shedding flow
obstacle according to FIG. 6, and
[0016] FIG. 9 is a representation of the operating principle of the
arrangement for the generation of modal sound fields.
DETAILED DESCRIPTION OF THE INVENTION
[0017] As shown in the drawings, flow obstacles 2 are arranged at
regular intervals on the inner circumference of a flow duct 1
which, according to FIGS. 1 to 3, have the form of rectangular,
equally long projections 10 with rounded edges. These projections
10 are located in only one cross-sectional plane and stick out
vertically from the flow duct inner wall. Accordingly, for the
generation of different modal sound fields, the flow obstacles 2
may also have other cross-sectional shapes, extend farther (or
lesser) into the flow duct interior, or, as shown in FIGS. 4 to 8,
be arranged on stays in the flow duct 1 or provided as cavities in
the flow duct wall (not shown). The cross-sectional shape of the
flow obstacles 2, in particular, is essential for the generation of
the sound field in the flow duct 1. Furthermore, the flow obstacles
2 in one and the same flow duct 1 may have different form. Finally,
the arrangement and quantity of the flow obstacles 2 is variable.
This means that the flow obstacles 2, individually or in a larger
number, may also be arranged in two or more cross-sectional planes
of the flow duct 1, and actually also be offset to each other (none
of these arrangements being shown). The positioning of the
obstacles may also be adjusted as desired to provide the desired
sound field. The flow duct can be constructed to allow quick and
easy variation of these factors to alter the sound field.
[0018] The flow duct 1 is passed by a fluid, here a gas, in the
direction of arrow 3. See FIGS. 2, 5 and 9. In a case of a
simulation of the sound field of a rotor-stator arrangement for a
gas turbine, compressor or similar machine, the fluid can be a hot
gas, a cold gas or a liquid. Sound propagates in the flow direction
3, as well as opposite to the flow direction 3, as indicated by the
arrows 4. In the variant shown in FIGS. 4 to 8, projections 11 with
two vortex shedding portions 11b each are provided as flow
obstacles 2 which are formed onto a stay 11a and are spaced from
each other and located remote of the duct inner wall. The stay 11a
is profiled such that, as shown in FIG. 7, essentially no vortices
will be shed by it.
[0019] The operation of the above described sound field generator
(aero-acoustic mode generator) for conversion of a portion of the
flow energy of the fluid into acoustic energy of a sound field
propagating in the direction of flow and opposite to the direction
flow is hereinafter described in light of FIG. 9.
[0020] On account of the flow, vortices 5 and 6 are periodically
shed at the flow obstacle 2 which, downstream of the flow obstacle
2, form a vortex path 7. The shedding frequency of the vortices 5,
6 depends on the flow velocity and the shape and size of the
respective flow obstacle 2. The alternating pressures produced by
the periodic vortex shedding create sounds which will propagate in
the flow duct 1 at and beyond a certain frequency (cut-on
frequency, resonant frequency). This frequency depends on the
geometry of the duct (cross-sectional shape, dimensions), the
velocity of flow and the gas temperature. The sounds produced by
the periodic shedding of vortices form an acoustic pressure field 8
in the flow duct 1, i.e. a modal sound field or at least an
acoustic mode with circumferentially and/or radially variable
amplitude which reacts synchronously on the flow obstacle 2 and on
the periodic shedding of vortices from the flow obstacle 2
(feedback loop according to arrow 9). A closed resonant loop is
created between vortex shedding and acoustic mode 8 as well as
between acoustic mode 8 and vortex shedding, i.e. the acoustic mode
imparts its frequency and phase on the vortex shedding, with a high
sound pressure level being generated by the synchronous feedback of
the modes on the shedding of vortices which is capable of
simulating certain noise situations in technical equipment, for
example in a rotor-stator arrangement, or which can be
used--phase-displaced--for active sound control, including
reduction and amplification of an existing sound pressure level.
The energy necessary for sound generation is extracted from the
energy of the flow medium, but this extraction of energy is
negligible and irrelevant for the operation of the technical
equipment under investigation, for example a rotor-stator
arrangement of a turbomachine.
[0021] To explain the operation in slightly different words, the
flow generates vortices downstream of the flow duct 1. The vortices
have a pressure field that is unsteady. This creates an acoustic
mode inside the flow duct 1 which has a spatial wavelength. The
mode synchronizes with the vortices and triggers separation of the
vortices at the trailing edges of the flow obstacles 2, thereby
creating a feedback loop. A portion of this energy can then be used
to actively reduce sound of another source.
LIST OF REFERENCE NUMERALS
[0022] 1 flow duct
[0023] 2 flow obstacle
[0024] 3 direction of flow, flow energy
[0025] 4 sound propagation direction, acoustic energy flow
[0026] 5 shed vortices
[0027] 6 shed vortices
[0028] 7 vortex path, aerodynamic sound source
[0029] 8 acoustic mode, modal sound field, pressure field
[0030] 9 feedback loop, feedback between 8 and 2
[0031] 10 projections with constant section
[0032] 11 projections with several vortex shedding portions
[0033] 11a stay
[0034] 11b vortex shedding portion
* * * * *